U.S. patent application number 12/044176 was filed with the patent office on 2008-09-18 for audio reproducing apparatus and audio reproducing method.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Takeshi FUJITA, Shinji KOJIMA, Seigo SUGUTA, Toshihiko TSUKUMA.
Application Number | 20080225658 12/044176 |
Document ID | / |
Family ID | 39762516 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080225658 |
Kind Code |
A1 |
SUGUTA; Seigo ; et
al. |
September 18, 2008 |
AUDIO REPRODUCING APPARATUS AND AUDIO REPRODUCING METHOD
Abstract
An audio reproducing apparatus of the present invention includes
the following: an extracting unit which extracts starting position
information from audio packets; a position calculating unit which
calculate, based on audio data information included in the audio
packets, a position of a starting audio frame; a first difference
calculating unit which calculates differences between positions
indicated in the starting position information which is extracted
by the extracting unit and positions calculated by the position
calculating unit; a first reproduction judging unit which judges
availability of reproduction for coded audio data based on a change
of each of the differences that is calculated by the first
difference calculating unit and is calculated for the respective
plural audio packets; and a decoding unit which decodes the coded
audio data in the case where the first reproduction judging unit
judges the coded audio data to be reproducible.
Inventors: |
SUGUTA; Seigo; (Nara,
JP) ; TSUKUMA; Toshihiko; (Osaka, JP) ;
FUJITA; Takeshi; (Osaka, JP) ; KOJIMA; Shinji;
(Osaka, JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
Osaka
JP
|
Family ID: |
39762516 |
Appl. No.: |
12/044176 |
Filed: |
March 7, 2008 |
Current U.S.
Class: |
369/47.14 |
Current CPC
Class: |
G11B 2020/10546
20130101; G11B 20/18 20130101; G11B 20/10527 20130101 |
Class at
Publication: |
369/47.14 |
International
Class: |
G11B 7/00 20060101
G11B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2007 |
JP |
2007-064048 |
Claims
1. An audio reproducing apparatus which decodes an audio data
stream including audio packets to be consecutively inputted, each
of the audio packets including: coded audio data which has been
coded and includes plural audio frames; starting position
information indicating a first position of a starting audio frame
among the plural audio frames; and audio data information which
indicates the coded audio data, said audio reproducing apparatus
comprising: an extracting unit operable to extract the starting
position information from the audio packet; a position calculating
unit operable to calculate, for the audio frame, a second position
indicating the starting audio frame among the plural audio frames
included in the audio packet, based on the audio data information
included in the audio packet; a first difference calculating unit
operable to calculate, on the audio packet basis, differences
between the respective first positions indicated in the starting
position information extracted by said extracting unit and the
respective second positions calculated by said position calculating
unit; a first reproduction judging unit operable to judge
availability of reproduction for the coded audio data, based on a
change in the differences calculated by said first difference
calculating unit, the differences being calculated for the audio
packets; and a decoding unit operable to selectively decode the
coded audio data in the case where said first reproduction judging
unit judges the coded audio data to be reproducible, and to not
decode the coded audio data in the case where said reproduction
judging unit judges the coded audio data to be irreproducible.
2. The audio reproducing apparatus according to claim 1, further
comprising: a first holding unit for holding the differences
calculated by said first difference calculating unit; a second
difference calculating unit operable to calculate a difference
between a difference calculated for a preceding audio packet out of
two audio packets included in the audio packets and held in said
first holding unit and a difference calculated for a succeeding
audio packet out of the two audio packets included in the audio
packets and calculated by said first difference calculating unit;
and a second holding unit for holding the differences calculated by
said second difference calculating unit, wherein said first
reproduction judging unit is operable to judge the coded audio data
to be: reproducible in the case where the differences held in said
second holding unit are constant; and irreproducible in the case
where the differences held in said second holding unit are not
constant.
3. The audio reproducing apparatus according to claim 1, further
comprising a first error judging unit operable to judge whether or
not the first positions indicated in the starting position
information extracted by said extracting unit match the
corresponding second positions calculated by said position
calculating unit, respectively, wherein said decoding unit is
operable to selectively: decode the coded audio data in the case
where said first error judging unit judges that the first positions
match the corresponding second positions, or in the case where said
first reproduction judging unit judges the coded audio data to be
reproducible; and not decode the coded audio data in the case where
said first error judging unit judges that the first positions do
not match the corresponding second positions, and said first
reproduction judging unit judges the coded audio data to be
irreproducible.
4. The audio reproducing apparatus according to claim 3, further
comprising a recovering unit operable to perform recovery
processing in the case where: said first error judging unit judges
that the first positions do not match the corresponding second
positions; and said first reproduction judging unit judges the
coded audio data to be irreproducible.
5. The audio reproducing apparatus according to claim 3,
comprising: a reproducing unit constructed in hardware and
including said extracting unit, said position calculating unit,
said first difference calculating unit, and said decoding unit; and
a control unit operable to control said reproducing unit, said
control unit including said first error judging unit and said first
reproduction judging unit, and being controlled by software,
wherein said reproducing unit further includes a notifying unit
operable to notify said control unit of the differences calculated
by said first difference calculating unit.
6. The audio reproducing apparatus according to claim 3,
comprising: a reproducing unit constructed in hardware, and
including said extracting unit, said position calculating unit,
said first difference calculating unit, said first error judging
unit, said reproduction judging unit, and said decoding unit; and a
control unit being controlled by software and operable to control
said reproducing unit.
7. The audio reproducing apparatus according to claim 6, wherein
said reproducing unit further includes a selecting unit operable to
select one of a first state and a second state, in the first state,
said first error judging unit is operable to judge whether or not
the first positions indicated in the starting position information
extracted by said extracting unit match the corresponding second
positions calculated by said position calculating unit,
respectively, in the first state, said first reproduction judging
unit is operable to judge the availability of the reproduction for
the coded audio data, based on the change in the differences
calculated by said first difference calculating unit, the
differences being calculated for the audio packets, said control
unit further includes: a second error judging unit operable to
judge, in the second state, whether or not the first positions
indicated in the starting position information extracted by said
extracting unit match the corresponding second positions calculated
by said position calculating unit, respectively; and a second
reproduction judging unit operable to judge, in the second state,
the availability of the reproduction for the coded audio data,
based on the change in the differences calculated by said first
difference calculating unit, the differences being calculated for
the audio packets, and in the first state, said decoding unit is
operable to selectively: decode the coded audio data in the case
where said first error judging unit judges the first positions
match the corresponding second positions, or in the case where said
first reproduction judging unit judges the coded audio data to be
reproducible; and not decode the coded audio data in the case where
said first error judging unit judges the first positions do not
match the corresponding second positions, and said first
reproduction judging unit judges the coded audio data to be
irreproducible, and in the second state, said decoding unit is
operable to selectively: decode audio data in the case where: said
second error judging unit judges the first positions match the
corresponding second positions; or in the case where said second
reproduction judging unit judges the coded audio data to be
reproducible; and not decode the coded audio data in the case where
said second error judging unit judges the first positions do not
match the corresponding second positions, and said second
reproduction judging unit judges the coded audio data to be
irreproducible.
8. The audio reproducing apparatus according to claim 1, wherein
the starting position information is included in the First Access
Unit Pointer.
9. The audio reproducing apparatus according to claim 1, wherein
the audio data information includes: information indicating a
quantization bit rate of the coded audio data; information
indicating a channel number of the coded audio data; and
information indicating a sampling frequency of the coded audio
data, and said position calculating unit is operable to calculate,
based on the quantization bit rate, the channel number, and the
sampling frequency, the first position of the starting audio frame
among the plural audio frames.
10. An audio reproducing method for an audio reproducing apparatus
which decodes an audio data stream including audio packets to be
consecutively inputted, each of the audio packets including: coded
audio data which has been coded and includes plural audio frames;
starting position information indicating a first position of a
starting audio frame among the plural audio frames; and audio data
information which indicates the coded audio data, said audio
reproducing method comprising: extracting the starting position
information from the audio packet; position calculating, for the
audio frame, a second position of the starting audio frame among
the plural audio frames included in the audio packet, based on the
audio data information included in the audio packet; a first
difference calculating, on the audio packet basis, differences
between the respective first positions indicated in the starting
position information extracted in said extracting and the
respective second positions calculated in said position
calculating; reproduction judging availability of reproduction for
the coded audio data, based on a change in the differences
calculated in said first difference calculating, the differences
being calculated for the audio packets; and selectively decoding
the coded audio data in the case where the coded audio data is
judged to be reproducible, and not decoding in the case where the
coded audio data is judged to be irreproducible.
11. A computer-readable program product for an audio reproducing
method for use in an audio reproducing apparatus which decodes an
audio data stream including audio packets to be consecutively
inputted, each of the audio packets including: coded audio data
which has been coded and includes plural audio frames; starting
position information indicating a first position of a starting
audio frame among the plural audio frames; and audio data
information which indicates the coded audio data, said program
product allowing, when loaded into the apparatus, the apparatus to
execute: extracting the starting position information from the
audio packet; position calculating, for the audio frame, a second
position of the starting audio frame among the plural audio frames
included in the audio packet, based on the audio data information
included in the audio packet; a first difference calculating, on
the audio packet basis, differences between the respective first
positions indicated in the starting position information extracted
in the extracting and the respective second positions calculated in
the position calculating; reproduction judging availability of
reproduction for the coded audio data, based on a change in the
differences calculated in the first difference calculating, the
differences being calculated for the audio packets; and selectively
decoding the coded audio data in the case where the coded audio
data is judged to be reproducible, and not decoding in the case
where the coded audio data is judged to be irreproducible.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] The present invention relates to audio reproducing
apparatuses and audio reproducing methods, and particularly to an
audio reproducing apparatus for decoding an audio data stream.
[0003] (2) Description of the Related Art
[0004] Audio reproducing apparatuses for reproducing audio data
detect errors based on various information when decoding the audio
data. For example, an audio reproducing apparatus detects an error
in the case where part of the data is damaged by a scratch on a
disc or a transmission error. In the case where the error is
detected, the audio reproducing apparatus performs recovery
processing in order to avoid noise.
[0005] For example, there are common techniques, which are used as
error detection approaches, for detecting abnormal data when
editing and recording the audio data (See Patent reference 1, for
example).
[0006] In addition, as audio data to be recorded in a music CD and
DVD, audio data coded (digitalized) by the Linear Pulse Code
Modulation (Linear PCM) scheme is used. Compared with compressed
audio data, the Linear PCM data has an extremely small amount of
information which can be used for the error detection. Thus, in the
Linear PCM data, the noise may possibly stay in the coded data in
the case where part of the data has been damaged by the scratch on
the disc and the transmission error. In order to avoid the noise,
the audio reproducing apparatus can detect the error, using the
First Access Unit Pointer in a DVD standard.
[0007] The following describes an error detecting process, in a
conventional audio reproducing apparatus, which uses the First
Access Unit Pointer.
[0008] In the DVD standard, there is a definition referred to as
the Access Unit (on a frame-to-frame basis, for example). The
Access Unit is used as a unit for the synchronization of video and
audio output. The First Access Unit Pointer is information showing
the starting position of the Access Unit (address) in a packet.
[0009] In order to judge whether or not a First Access Unit Pointer
value is valid, the audio reproducing apparatus confirms the First
Access Unit Pointer value included in the inputted data and a
position of a First Access Unit (starting position of an Access
Unit in a packet), which is calculated out of the actual data
amount. In the case where a shift occurs between the First Access
Unit Pointer value included in the inputted data and the position
of the First Access Unit calculated out of the actual data amount,
the audio reproducing apparatus performs recovery processing in
order to avoid producing noise, i.e. discarding currently read-out
data once, initializing the reproducing unit, and then restarting
the reproducing apparatus. By doing so, the audio reproducing
apparatus can avoid the noise resulting from the data shift.
[0010] Meanwhile, since the DVD has become popular, DVD format data
can be created on a personal computer and recorded in a medium such
as a DVD-R. Out of tools creating the DVD format data on a marketed
PC, some of the tools create DVD format data which does not conform
to the DVD standard. Among the DVD format data which does not
conform to the standard, there exists data having the
above-mentioned First Access Unit Pointer value accidentally
assigned. The data violating the standard can normally be
reproduced unless the accidentally assigned First Access Unit
Pointer value is used since the audio data itself is properly
recorded.
[0011] However, when reproducing the Linear PCM data which has been
recorded in the DVD, the conventional audio reproducing apparatus
confirms the shift between the First Access Unit Pointer value in
the Linear PCM data recorded in the DVD and the position of the
First Access Unit calculated out of the actual data amount. Thus,
in the case where the conventional audio reproducing apparatus
tries to reproduce the data having the value of the First Access
Unit Pointer accidentally assigned, the apparatus always judges the
data to be an error and repeats an error recovery process. In other
words, the conventional audio reproducing apparatus fails to
reproduce successfully the data having the value of the First
Access Unit Pointer accidentally assigned.
[0012] More specifically, the problem is that the conventional
audio reproducing apparatus fails to reproduce audio data which
does not conform to the DVD standard. [0013] Patent reference 1:
Japanese Unexamined Patent Application Publication No.
2002-025232.
SUMMARY OF THE INVENTION
[0014] In view of the above problems, the objective of the present
invention is to provide an audio reproducing apparatus which can
reproduce audio data that does not conform to the DVD standard and
the audio reproducing method of the same.
[0015] In order to achieve the above objectives, the audio
reproducing apparatus, of the present invention, decodes an audio
data stream including audio packets to be consecutively inputted,
each of the audio packets including: coded audio data which has
been coded and includes plural audio frames; starting position
information indicating a first position of a starting audio frame
among the plural audio frames; and audio data information which
indicates the coded audio data, the audio reproducing apparatus
including: an extracting unit which extracts the starting position
information from the audio packet; a position calculating unit
which calculates, for the audio frame, a second position indicating
the starting audio frame among the plural audio frames included in
the audio packet, based on the audio data information included in
the audio packet; a first difference calculating unit which
calculates, on the audio packet basis, differences between the
respective first positions indicated in the starting position
information extracted by the extracting unit and the respective
second positions calculated by the position calculating unit; a
first reproduction judging unit which judges availability of
reproduction for the coded audio data, based on a change in the
differences calculated by the first difference calculating unit,
the differences being calculated for the audio packets; and a
decoding unit which selectively decodes the coded audio data in the
case where the first reproduction judging unit judges the coded
audio data to be reproducible, and to not decode the coded audio
data in the case where the reproduction judging unit judges the
coded audio data to be irreproducible.
[0016] According to this structure, the first reproduction judging
unit judges the availability of reproduction for the coded audio
data based on the change in the differences calculated for the
audio packets by the first difference calculating unit. Here, when
the position indicated in the starting position information is an
unauthorized value because of violation, the change in the
differences calculated for the audio packets by the first
difference calculating unit has regularity. Thus, based on the
change in the differences calculated for the audio packets by the
first difference calculating unit, the audio reproducing apparatus
in the present invention can judge the fact that the position
indicated in the starting position information is the unauthorized
value due to either the violation or a destruction of the data
caused by a scratch on a disc or a transmission error. As a result,
the audio reproducing apparatus in the present invention can
reproduce audio data which does not conform to the DVD standard,
without judging the audio data to be an error. Stated differently,
the present invention can provide the audio reproducing apparatus
which can reproduce the audio data that does not conform to the DVD
standard.
[0017] Further, based on the position of the starting audio frame
shown with the starting position information and the position of
the starting audio frame calculated by the position calculating
unit, the audio reproducing apparatus in the present invention can
judge whether or not the starting position information is the
unauthorized value. Thus, the audio reproducing apparatus in the
present invention can detect the starting position information to
be the unauthorized value because of the scratch on the disc or the
transmission error as an error. This allows the audio reproducing
apparatus in the present invention to prevent a noise caused by the
scratch on the disc or the transmission error.
[0018] In addition, the audio reproducing apparatus may further
include: a first holding unit for holding the differences
calculated by the first difference calculating unit; a second
difference calculating unit which calculates a difference between a
difference calculated for a preceding audio packet out of two audio
packets included in the audio packets and held in the first holding
unit and a difference calculated for a succeeding audio packet out
of the two audio packets included in the audio packets and
calculated by the first difference calculating unit; and a second
holding unit for holding the differences calculated by the second
difference calculating unit, wherein the first reproduction judging
unit may judge the coded audio data to be: reproducible in the case
where the differences held in the second holding unit are constant;
and irreproducible in the case where the differences held in the
second holding unit are not constant.
[0019] According to this structure, the second difference
calculating unit calculates changes (differences) of differences
between consecutive audio packets, calculated by the first
difference calculating unit. In the case where the changes
(differences) calculated by the second difference calculating unit
are constant, the first reproduction judging unit judges the coded
audio data to be reproducible. Here, when the position indicated in
the starting position information is the unauthorized value because
of the violation, the changes calculated by the second difference
calculating unit are constant. Based on the fact whether or not the
changes are constant in the differences between: the position
indicated in the starting position information between consecutive
audio packets; and the position calculated by the position
calculation unit, the audio reproducing apparatus in the present
invention can, therefore, judge whether or not the position
indicated in the starting position information is the unauthorized
value due to either the violation or the scratch on the disc or the
destruction of the data. As a result, the audio reproducing
apparatus in the present invention can reproduce the audio data
which does not conform to the standard, without judging the audio
data to be an error.
[0020] Furthermore, the audio reproducing apparatus may further
include a first error judging unit which judges whether or not the
first positions indicated in the starting position information
extracted by the extracting unit match the corresponding second
positions calculated by the position calculating unit,
respectively, wherein the decoding unit may selectively: decode the
coded audio data in the case where the first error judging unit
judges that the first positions match the corresponding second
positions, or in the case where the first reproduction judging unit
judges the coded audio data to be reproducible; and not decode the
coded audio data in the case where the first error judging unit
judges that the first positions do not match the corresponding
second positions, and the first reproduction judging unit judges
the coded audio data to be irreproducible.
[0021] According to this structure, the first error judging unit
judges whether or not the positions of the starting audio frames
indicated in the starting position information match the respective
positions, which are calculated by the position calculating unit,
of the starting audio frames. This allows the audio reproducing
apparatus in the present invention to judge whether or not the
starting position information is unauthorized value. Thus, the
audio reproducing apparatus in the present invention can detect the
starting position information to be the unauthorized value because
of the scratch on the disc or the transmission error as an error.
This allows the audio reproducing apparatus in the present
invention to prevent a noise caused by the scratch on the disc or
the transmission error.
[0022] Moreover the audio reproducing apparatus may further include
a recovering unit which performs recovery processing in the case
where: the first error judging unit judges that the first positions
do not match the corresponding second positions; and the first
reproduction judging unit judges the coded audio data to be
irreproducible.
[0023] According to this structure, when the starting position
information is the unauthorized value because of the scratch on the
disc or the transmission error, the recovering unit performs
recovery processing, i.e. discarding once currently read-out data,
and initializing and restarting the reproducing unit. This prevents
the noise caused by the scratch on the disc or the transmission
error.
[0024] In addition, the audio reproducing apparatus may include: a
reproducing unit constructed in hardware and including the
extracting unit, the position calculating unit, the first
difference calculating unit, and the decoding unit; and a control
unit which controls the reproducing unit, the control unit
including the first error judging unit and the first reproduction
judging unit, and being controlled by software, wherein the
reproducing unit may further include a notifying unit which
notifies the control unit of the differences calculated by the
first difference calculating unit.
[0025] According to this structure, the control unit, controlled by
software, controls whether or not the reproduction is to be
continued. Thus, the audio reproducing apparatus in the present
invention can perform error recovery processing which is suitable
to a system.
[0026] Furthermore, the audio reproducing apparatus may include: a
reproducing unit constructed in hardware, and including the
extracting unit, the position calculating unit, the first
difference calculating unit, the first error judging unit, the
reproduction judging unit, and the decoding unit; and a control
unit which is controlled by software and controls the reproducing
unit.
[0027] According to this structure, the reproducing unit
constructed in hardware controls whether or not the reproduction is
to be continued. Thus, the audio reproducing apparatus in the
present invention can perform error recovery processing without
overloading the control unit, such as a CPU.
[0028] Moreover, the reproducing unit may further include a
selecting unit which selects one of a first state and a second
state, in the first state, the first error judging unit may judge
whether or not the first positions indicated in the starting
position information extracted by the extracting unit match the
corresponding second positions calculated by the position
calculating unit, respectively, in the first state, the first
reproduction judging unit may judge the availability of the
reproduction for the coded audio data, based on the change in the
differences calculated by the first difference calculating unit,
the differences being calculated for the audio packets, the control
unit may further include: a second error judging unit which judges,
in the second state, whether or not the first positions indicated
in the starting position information extracted by the extracting
unit match the corresponding second positions calculated by the
position calculating unit, respectively; and a second reproduction
judging unit which judges, in the second state, the availability of
the reproduction for the coded audio data, based on the change in
the differences calculated by the first difference calculating
unit, the differences being calculated for the audio packets, and
in the first state, the decoding unit may selectively: decode the
coded audio data in the case where the first error judging unit
judges the first positions match the corresponding second
positions, or in the case where the first reproduction judging unit
judges the coded audio data to be reproducible; and not decode the
coded audio data in the case where the first error judging unit
judges the first positions do not match the corresponding second
positions, and the first reproduction judging unit judges the coded
audio data to be irreproducible, and in the second state, the
decoding unit may selectively: decode audio data in the case where:
the second error judging unit judges the first positions match the
corresponding second positions; or in the case where the second
reproduction judging unit judges the coded audio data to be
reproducible; and not decode the coded audio data in the case where
the second error judging unit judges the first positions do not
match the corresponding second positions, and the second
reproduction judging unit judges the coded audio data to be
irreproducible.
[0029] According to this structure, the selecting unit selects one
of the first state and the second state. In the first state, the
reproducing unit constructed in hardware controls whether or not
the reproduction is to be continued. In the second state, the
control unit controlled by software controls whether or not the
reproduction is to be continued. Thus, the audio reproducing
apparatus in the present invention can judge whether or not the
reproduction is to be continued and perform the recovery processing
with the most appropriate scheme for the system, providing an
interface of which an operation mode is addressable.
[0030] In addition, the starting position information may be
included in the First Access Unit Pointer.
[0031] According to this structure, the audio reproducing apparatus
in the present invention can judge whether or not the First Access
Unit Pointer is the unauthorized value based on the position of the
starting audio frame indicated in the First Access Unit Pointer and
the position of the starting audio frame calculated by the position
calculating unit. Thus, in the Liner PCM data having a little
information for error detection, the audio reproducing apparatus in
the present invention can detect the starting position information
to be the unauthorized value because of the scratch on the disc or
the transmission error as an error. This allows the audio
reproducing apparatus in the present invention to avoid the noise
in the Liner PCM data.
[0032] Moreover, the audio reproducing apparatus in the present
invention judges the availability of reproducing the coded audio
data based on the change of the differences calculated for the
audio packets by the first difference calculating unit. Thus, the
audio reproducing apparatus in the present invention can judge the
position indicated in the First Access Unit Pointer is to be the
unauthorized value due to either the violation or the destruction
of the data caused by the scratch on the disc or the transmission
error. This allows the audio reproducing apparatus in the present
invention to reproduce the audio data which does not conform to the
standard, without judging the audio data to be an error.
[0033] Furthermore, the audio data information may include:
information indicating a quantization bit rate of the coded audio
data; information indicating a channel number of the coded audio
data; and information indicating a sampling frequency of the coded
audio data, and the position calculating unit may calculate, based
on the quantization bit rate, the channel number, and the sampling
frequency, the first position of the starting audio frame among the
plural audio frames.
[0034] According to this structure, the position of the starting
audio frame can be calculated out of the information included in
the audio packets.
[0035] In addition, an audio reproducing method for an audio
reproducing apparatus, in the present invention, which decodes an
audio data stream including audio packets to be consecutively
inputted, each of the audio packets including: coded audio data
which has been coded and includes plural audio frames; starting
position information indicating a first position of a starting
audio frame among the plural audio frames; and audio data
information which indicates the coded audio data, the audio
reproducing method including: extracting the starting position
information from the audio packet; position calculating, for the
audio frame, a second position of the starting audio frame among
the plural audio frames included in the audio packet, based on the
audio data information included in the audio packet; a first
difference calculating, on the audio packet basis, differences
between the respective first positions indicated in the starting
position information extracted in the extracting and the respective
second positions calculated in the position calculating;
reproduction judging availability of reproduction for the coded
audio data, based on a change in the differences calculated in the
first difference calculating, the differences being calculated for
the audio packets; and selectively decoding the coded audio data in
the case where the coded audio data is judged to be reproducible,
and not decoding in the case where the coded audio data is judged
to be irreproducible.
[0036] According to this, in the reproduction judging, the
availability of reproduction for the coded audio data is judged
based on the change in the differences calculated for the audio
packets by the first difference calculating. Here, when the
position indicated in the starting position information is an
unauthorized value because of violation, the change in the
differences calculated for the audio packets by the first
difference calculating has regularity. Thus, based on the change in
the differences calculated for the audio packets by the first
difference calculating, the audio reproducing method in the present
invention can judge the fact that the position indicated in the
starting position information is the unauthorized value due to
either the violation or a destruction of the data caused by a
scratch on a disc or a transmission error. As a result, the audio
reproducing method in the present invention is intended for
reproducing audio data which does not conform to the DVD standard,
without judging the audio data to be an error. Stated differently,
the present invention can provide the audio reproducing method
which makes it possible to reproduce the audio data that does not
conform to the DVD standard.
[0037] Further, based on the position of the starting audio frame
indicated in the starting position information and the position of
the starting audio frame calculated by the position calculating,
the audio reproducing method in the present invention is intended
for judging whether or not the starting position information is the
unauthorized value. Thus, the audio reproducing method in the
present invention is intended for detecting the starting position
information to be the unauthorized value because of the scratch on
the disc or the transmission error as an error. This makes the
audio reproducing method in the present invention possible to
prevent a noise caused by the scratch on the disc or the
transmission error.
[0038] Note that the present invention can not only be implemented
as the audio reproducing apparatus and the audio reproducing method
mentioned above, but also be implemented as a program causing a
computer to execute a characteristic step included in the audio
reproducing apparatus. Such a program can be distributed through a
storage medium such as a CD-ROM and the like and a transmission
medium such as the Internet and the like.
[0039] As mentioned above, the present invention provides the audio
reproducing apparatus which can reproduce the audio data that does
not conform to the standard and the audio reproducing method for
use in reproducing the audio data that does not conform to the
standard possible.
FURTHER INFORMATION ABOUT TECHNICAL BACKGROUND TO THIS
APPLICATION
[0040] The disclosure of Japanese Patent Application No.
2007-064048 filed on Mar. 13, 2007 including specification,
drawings and claims is incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] These and the other objects, advantages and features of the
invention will become apparent from the following description
thereof taken in conjunction with the accompanying drawings which
illustrate a specific embodiment of the invention. In the
drawings:
[0042] FIG. 1 is a block diagram illustrating a structure of an
audio reproducing apparatus in a first embodiment of the present
invention;
[0043] FIG. 2 is a diagram illustrating a structure of a Linear PCM
audio packet in the DVD-Video standard;
[0044] FIG. 3 is a flowchart showing a flow of processing in an
error detecting unit in the audio reproducing apparatus in the
first embodiment of the present invention;
[0045] FIG. 4 is a flowchart showing a flow of processing in a
control unit in the audio reproducing apparatus in the first
embodiment of the present invention;
[0046] FIG. 5 is a block diagram illustrating a structure of an
audio reproducing apparatus in a second embodiment of the present
invention;
[0047] FIG. 6 is a flowchart showing a flow of processing in an
error detecting unit in the audio reproducing apparatus in the
second embodiment of the present invention;
[0048] FIG. 7 is a block diagram illustrating a structure of an
audio reproducing apparatus in a third embodiment of the present
invention; and
[0049] FIG. 8 is a flowchart showing a flow of processing in an
error detecting unit in the audio reproducing apparatus in the
third embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] Embodiments of the present invention are described below in
detail with reference to the drawings.
First Embodiment
[0051] An audio reproducing apparatus in the first embodiment of
the present invention judges an error based on a change of a shift
between a value of a First Access Unit Pointer included in audio
data and a position of a First Access Unit calculated out of actual
data amount, which enables a judgment in that whether the error
occurs either by noise or violation of a standard in music data.
Thus, the audio reproducing apparatus in the first embodiment of
the present invention can reproduce the music data which violates
the standard.
[0052] First, a structure of the audio reproducing apparatus in the
first embodiment of the present invention is described.
[0053] FIG. 1 is a block diagram illustrating the structure of the
audio reproducing apparatus in the first embodiment of the present
invention.
[0054] An audio reproducing apparatus 100 illustrated in FIG. 1
reproduces audio data recorded in a DVD and the like. The audio
reproducing apparatus 100 decodes an audio data stream 131 and
outputs the decoded audio data stream 131 as decoded audio data
133. The audio data stream 131 is a digitalized Linear PCM audio
stream in the DVD-Video standard. In other words, the audio data
stream 131 includes plural audio packets which are consecutively
stream inputted. The audio reproducing apparatus 100 includes a
control unit 101 and a reproducing unit 102.
[0055] A structure of the audio data stream 131 shall be described
as follows.
[0056] FIG. 2 is a diagram illustrating a structure of the Linear
PCM audio packet in the DVD-Video scheme.
[0057] A Linear PCM audio packet 150 illustrated in FIG. 2 includes
a packet header 151, a Sub_stream_id 152, audio frame information
153, audio data information 154, and audio data 155.
[0058] The packet header 151 includes information on the kind of
the packet and the length of the data. For example, the packet
header 151 includes information that each of audio packets 150 is
an audio data stream.
[0059] The Sub_stream_id 152 is information indicating the kind of
the packet. For example, the Sub_stream_id 152 is information
indicating the fact that the audio packet 150 is an audio data
stream in the Linear PCM scheme.
[0060] The audio data 155 is audio data coded with the Linear PCM
scheme, and includes plural audio frames 167.
[0061] The audio frame information 153 is information on the plural
audio frames 167 which are included in the audio data 155. The
audio frame information 153 includes a Number_of_frame_header 156
and a First_access_unit_pointer 157.
[0062] The Number_of_frame_header 156 is information showing the
number of the headers with the audio frames 167 included in the
audio data 155. In other words, the Number_of_frame_header 156
shows the number of the audio frames 167 included in the audio data
155.
[0063] The First_access_unit_pointer 157 is information showing the
starting position of the first audio frame among the succeeding
audio frames 167 included in the audio packet 150. In other words
the First_access_unit_pointer 157 is information showing the
address of the first audio frame 167 to be accessed among the
plural audio frames 167 included in the audio data 155.
[0064] The audio data information 154 is information on the audio
data 155. The audio data information 154 includes Audio_emphasis
158, Audio_mute 159, reserved 160, Audio_frame_number 161,
Quantization_word_length 162, Audio_sampling_frequency 163,
reserved 164, Number_of_audio_channels 165, and
Dynamic_range_control 166.
[0065] The Audio_emphasis 158 is information indicating whether or
not the audio data 155 is pre-emphasized.
[0066] The Audio_mute 159 is information showing whether the mute
on the audio reproducing apparatus is on-state or off-state.
[0067] The Audio_frame_number 161 is the frame number which the
first audio frame 167 to be accessed has.
[0068] The Quantization_word_length 162 is information showing the
number of bits to quantize the audio data 155. In other words, the
Quantization_word_length 162 shows the quantization bit rate of the
audio data 155. For example, the Quantization_word_length 162
provides information on the quantization bit rate of the audio data
155, for example, 16 bits, 20 bits, and 24 bits.
[0069] The Audio_sampling_frequency 163 is information showing the
sampling frequency of the audio data 155. For example, the
Audio_sampling_frequency 163 provides information on the sampling
frequency of the audio data 155, i.e. 48 kHz or 96 kHz.
[0070] The Number_of_audio_channels 165 is information showing the
number of the audio channels, a channel number.
[0071] The Dynamic_range_control 166 is control information on a
Dynamic range.
[0072] The reproducing unit 102 decodes the audio data stream 131,
as well as detects an error therein. The reproducing unit 102 is
constructed in a dedicated circuit (hardware) to the unit. For
example, the reproducing unit 102 is a semi-conductor integrated
circuit structured of one or more chips. The reproducing unit 102
includes an error detecting unit 103 and a decoding unit 104.
[0073] The error detecting unit 103 detects the error in the audio
data stream 131.
[0074] The error detecting unit 103 includes an extracting unit
111, a calculating unit 112, a first difference calculating unit
113, and a notifying unit 114.
[0075] The decoding unit 104 decodes the audio data 155 included in
the audio data stream 132 and outputs the decoded audio data 155 as
the decoded audio data 133. Here, the audio data stream 132, which
is the same signal as the audio data stream 131, is a digital audio
data stream outputted via the error detecting unit 103.
[0076] The control unit 101 controls the reproducing unit 102.
Meanwhile, the control unit 101 is controlled by the software, that
is, the control unit 101 implements the functions shown in FIG. 1,
executing the program. For example, either a micro computer or a
CPU can be the control unit 101. The control unit 101 includes a
first judging unit 121, a first holding unit 122, a second
difference calculating unit 123, a second holding unit 124, a
second judging unit 125, a decoding control unit 126, and a
recovering unit 127.
[0077] The extracting unit 111 extracts the
First_access_unit_pointer 157 from the audio packet 150 included in
the audio data stream 131.
[0078] The calculating unit 112 calculates .beta., the position of
the starting audio frame 167 among the plural audio frames 167
included in the audio packet 150, out of the audio data information
154 included in the audio packet 150. Specifically, the calculating
unit 112 calculates .beta., the position of the starting audio
frame 167, based on the Quantization_word_length 162, the
Audio_sampling_frequency 163, and the Number_of_audio_channels
165.
[0079] The first difference calculating unit 113 calculates a
difference Diff between the position .alpha. and the position
.beta.. Here, the position .alpha. is the position of the starting
audio frame 167 shown with the First_access_unit_pointer 157 which
is extracted from the extracting unit 111, and the position .beta.
is the position of the starting audio frame 167 calculated by the
calculating unit 112.
[0080] The notifying unit 114 notifies the control unit 101 of each
of differences Diff calculated by the first difference calculating
unit 113.
[0081] The first judging unit 121 judges whether or not the
position .alpha. matches with the position .beta.. Here, the
position .alpha. is the position shown with the
First_access_unit_pointer 157 which is extracted from the
extracting unit 111, and the position .beta. is the position
calculated by the calculating unit 112 is identical. For example,
the first judging unit 121 judges that the position .alpha.:
matches with the position .beta. when the difference Diff notified
by the notifying unit 114 is "0"; and does not match the position
.beta. when the difference Diff is other than "0".
[0082] The first holding unit 122 holds the difference Diff which
has been calculated by the first difference calculating unit 113
and notified by the notifying unit 114. The first holding unit 122
also holds the differences Diff each of which is calculated for the
respective plural audio packets 150 to be inputted
consecutively.
[0083] The second difference calculating unit 123 calculates a
difference Diff between succeeding two audio packets. Specifically,
the second difference calculating unit 123 calculates a difference
.DELTA.. Each of differences .DELTA. is a difference between: the
difference Diff which is calculated for the preceding audio packet
of the two consecutive audio packets and is held in the first
holding unit 122; and the difference Diff which is calculated for
the second audio packet 150 of the two consecutive audio packets
150 and calculated by the first difference calculating unit 113. In
other words, the second difference calculating unit 123 calculates
the differences .DELTA. each of which is the change of the
respective differences Diff between the plural audio packets 150 to
be consecutively inputted.
[0084] The second holding unit 124 holds plural differences
.DELTA., including the difference .DELTA., which are calculated by
the second difference calculating unit 123.
[0085] In the case where the first judging unit 121 judges that the
position .alpha. does not match the position .beta., the second
judging unit 125 judges availability of the reproduction for the
audio data 155 included in the audio data stream 131 according to
the change of the differences Diff which are calculated by the
first difference calculating unit 113 and each of which calculated
for the respective plural audio packets 150. Specifically, in the
case where the plural differences .DELTA. held in the second
holding unit 124 are constant, the second judging unit 125 judges
the audio data 155, included in the audio data stream 131, to be
reproducible. In the case where the plural differences .DELTA. held
in the second holding unit 124 are not constant, the second judging
unit 125 judges the audio data 155, included in the audio data
stream 131, to be irreproducible. In other words, the second
judging unit 125 judges the audio data 155 to be: reproducible when
the plural differences .DELTA. between the consecutive audio
packets 150 are constant; and irreproducible when the plural
differences .DELTA. not constant.
[0086] Based on judgment results obtained from the first judging
unit 121 and the second judging unit 125, the decoding control unit
126 controls decode processing on the audio data stream 132, the
decode processing which is performed by the decoding unit 104.
Specifically, when the first judging unit 121 judges that the
position .alpha. extracted by the extracting unit 111 matches with
the position .beta. calculated by the calculating unit 112, the
decoding unit 104, controlled by the decoding control unit 126,
decodes the audio data 155 included in the audio data stream 132.
In the case where: the first judging unit 121 judges the position
.alpha. does not match the position .beta.; and the second judging
unit 125 judges the audio data 155 to be reproducible, then the
decoding unit 104, controlled accordingly by the decoding control
unit 126, decodes the audio data 155 included in the audio data
stream 132. In the case where: the first judging unit 121 judges
that the position .alpha. does not match the position .beta.; and
the second judging unit 125 judges the audio data 155 to be
irreproducible, then the decoding unit 104, controlled accordingly
by the decoding control unit 126, does not decode the audio data
155 included in the audio data stream 132.
[0087] The recovering unit 127 performs recovery processing when
the first judging unit 121 judges that the position .alpha. does
not match the position .beta. and the second judging unit 125
judges the audio data 155 to be irreproducible. Specifically, the
recovery processing performed by the recovering unit 127 is to
discard once currently read out data, and initialize and restart
the reproducing unit 102.
[0088] Next, operations of the audio reproducing apparatus 100 in
the first embodiment of the present invention are described.
[0089] FIG. 3 is a flowchart showing a flow of processing in the
error detecting unit 103.
[0090] As shown in the FIG. 3, first, the extracting unit 111
extracts the position .alpha.; that is, the position of the
starting audio frame 167 shown with the First_access_unit_pointer
157 which is included in the audio data stream 131 (S101).
[0091] Next, the calculating unit 112 calculates the position
.beta.; that is, the position of the starting audio frame 167
calculated out of the audio data information 154 (S102).
Specifically, the calculating unit 112 calculates, out of the
Audio_sampling_frequency 167 (sampling frequency), a sample number
included in one audio frame 167 (80, for example). The calculating
unit 112 calculates a data size of the one audio frame 167 out of
the Quantization_word_length 162, the calculated sample number (80,
for example), and the Number_of_audio_channel 165 (the quantization
bit rate by the sample number by the channel number). The
calculating unit 112 calculates the position .beta., the position
of the starting audio frame 167 included in the audio packet 150,
by accumulating the data sizes from the beginning of the processing
start.
[0092] Next, the first difference calculating unit 113 calculates
the difference Diff between the position .alpha. and the position
.beta.. Here, the position .alpha. is the position of the starting
audio frame 167 shown with the First_access_unit_pointer 157 which
is extracted from the extracting unit 111, and the position .beta.
is the position of the starting audio frame 167 calculated by the
calculating unit 112 (S103).
[0093] Next, the notifying unit 114 notifies the control unit 101
of the difference Diff calculated by the first difference
calculating unit 113 (S104).
[0094] FIG. 4 is the flowchart showing the flow of the processing
in the control unit 101.
[0095] As shown in FIG. 4, the control unit 101 obtains the
difference Diff which has been notified by the notifying unit 114
(S201). The first holding unit 122 holds the difference Diff which
has been notified by the notifying unit 114.
[0096] The first judging unit 121 judges whether or not the
position .alpha. matches with the position .beta. (S202). In the
case where the first judging unit 121 judges that the position
.alpha. matches with the position .beta. (S202: Yes); that is, the
position .alpha. shown with the First_access_unit_pointer 157 is
correct, the decoding unit 104, controlled by the decoding control
unit 126, decodes the audio data stream 132. In other words, the
audio reproducing apparatus 100 continues reproduction processing
(S206).
[0097] In the meantime, when the first judging unit 121 judges that
the position .alpha. does not match the position .beta. (S202: No);
that is, the position .alpha. shown with the
First_access_unit_pointer 157 is not correct, the second difference
calculating unit 123 calculates the difference .DELTA. (S203).
Here, the difference .DELTA. is a difference between a difference
Diff_old which is calculated for the immediately preceding audio
packet 150 and is held in the first holding unit 122 and the
difference Diff which has been newly calculated and held in the
first holding unit 122 (S203). The second holding unit 124 holds
the difference .DELTA. calculated by the second difference
calculating unit 123.
[0098] Next, the first holding unit 122 holds the newly calculated
difference Diff as the difference Diff_old (S204).
[0099] Then, the second judging unit 125 judges whether or not the
plural differences .DELTA. held in the second holding unit 124 are
constant (S205). Specifically, the second judging unit 125 judges
the audio data stream 131 to be reproducible when the plural
differences .DELTA. held in the second holding unit 124 are
constant; that is, the respective differences .DELTA. between the
plural audio packets to be consecutively inputted are constant
(S205: Yes). Furthermore, the second judging unit 125 judges the
audio data stream 131 to be irreproducible when the plural
differences .DELTA. held in the second holding unit 124 vary; that
is, the respective differences .DELTA. between the plural audio
packets to be consecutively inputted not constant (S205: No).
[0100] Here, there is a case where a value of the
First_access_unit_pointer 157 is in the violation of the standard
when the audio data stream 131 is data created on a PC encoder. In
addition, when the data violates the standard, each value of the
differences Diff shifts by constant change between the consecutive
audio packets. In other words, the differences .DELTA. between the
plural audio packets to be consecutively inputted are constant.
[0101] On the other hand, in the case where the value of the
First_access_unit_pointer 157 is unauthorized due to destruction of
part of the data caused by a scratch on a disc or a transmission
error, the difference Diff changes on an irregular basis. In other
words, the differences .DELTA. between plural audio packets to be
consecutively inputted vary respectively, and are not constant.
[0102] Through the above mentioned fact, the audio reproducing
apparatus 100 in the first embodiment of the present invention
judges whether or not the plural differences .DELTA. held in the
second holding unit 124 are constant. As the result, a value of the
First_access_unit_pointer 157 is judged to be unauthorized because
either the value is in the violation of the standard, or the data
is damaged.
[0103] In the case where the differences .DELTA. are constant
(S205: Yes), the decoding unit 104, controlled accordingly by the
decoding control unit 126, decodes the audio data stream 132. In
other words, the audio reproducing apparatus 100 continues
reproduction processing (S206).
[0104] Meanwhile, in the case where the differences .DELTA. are not
constant (S205: No), the decoding unit 104, controlled accordingly
by the decoding control unit 126, halts the decoding of the audio
data stream 132. Furthermore, the recovering unit 127 discards once
currently read out data, and performs recovery processing such as
initialization and restart of the reproducing unit 102 (S207).
[0105] Following one of the reproduction continuation (Step S206)
and recovery processing (Step S207), the audio reproducing
apparatus 100 applies processing, shown in FIG. 3 and FIG. 4, to
the succeeding audio packets 150.
[0106] Through the above operations, the audio reproducing
apparatus 100 in the first embodiment of the present invention
calculates, based on the audio data information 154, the position
.beta. of the starting audio frame 167. The first difference
calculating unit 113 calculates the difference Diff between the
position .alpha., indicating the position of the starting audio
frame 167 shown with the First_access_unit_pointer 157, and the
position .beta.. The second difference calculating unit 123
calculates the differences .DELTA. each of which is the change of
the respective differences Diff between the consecutive audio
packets. When the differences .DELTA. are constant, the second
judging unit 125 judges the First_access_unit_pointer 157 to be
unauthorized due to the violation of the standard. Moreover, when
the differences .DELTA. are not constant, the second judging unit
125 judges the First_access_unit_pointer 157 to be unauthorized due
to the destruction of the data.
[0107] Through the above mentioned process, the audio reproducing
apparatus 100 in the first embodiment of the present invention
judges the value of the First_access_unit_pointer 157 to be
unauthorized because either the value is in the violation of the
standard, or the data is damaged. Thus, the audio reproducing
apparatus 100 in the first embodiment of the present invention can
avoid the noise generated resulting from data shift which is caused
by the scratch on the disc or the transmission error and damages
part of the data. In addition, the audio reproducing apparatus 100
in the first embodiment of the present invention can reproduce the
music data which conventional audio reproducing apparatuses judge
to be an error and does not conform to the standard.
[0108] Furthermore, the audio reproducing apparatus 100 in the
first embodiment of the present invention judges the value of the
First_access_unit_pointer 157 to be authorized in the case where
the position .alpha. matches with the position .beta.. As a result,
when the value of the First_access_unit_pointer 157 is authorized,
the audio reproducing apparatus 100 in the first embodiment of the
present invention can continue reproduction processing.
[0109] Moreover, the audio reproducing apparatus 100 in the first
embodiment of the present invention, by the control unit 101 which
is under the control of the software, controls whether or not: the
reproduction is to be continued; and the recovery processing is
performed. As a result, the audio reproducing apparatus 100 in the
first embodiment of the present invention can perform error
recovery processing which is suitable to a system.
[0110] Note that in the above description, the decoding unit 104 is
intended to decode the audio data stream 132 which is the audio
data stream 131 inputted via the error detecting unit 103; however,
the decoding unit 104 may also decode the audio data stream
131.
[0111] Furthermore, in the above description, the extracting unit
111, the calculating unit 112, and the first difference calculating
unit 113 intend to be included in the reproducing unit 102 which is
constructed in hardware; however, all or part of the extracting
unit 111, the calculating unit 112, and the first difference
calculating unit 113 may be implemented in the form of software. In
addition, all or part of the extracting unit 111, the calculating
unit 112, and the first difference calculating unit 113 may be
included in the control unit 101.
[0112] Moreover, the above description intends the first judging
unit 121, the first holding unit 122, the second difference
calculating unit 123, the second holding unit 124, the second
judging unit 125, the decoding control unit 126, and the recovering
unit 127 to be included in the control unit 101 which is controlled
by the software; however, part of the first judging unit 121, the
first holding unit 122, the second difference calculating unit 123,
the second holding unit 124, the second judging unit 125, the
decoding control unit 126, and the recovering unit 127 may also be
constructed in hardware. For example, the first holding unit 122
and the second holding unit 124 may be a RAM, a non-volatile
memory, or a hard disc which the audio reproducing apparatus 100
provides. Furthermore, part of the first judging unit 121, the
first holding unit 122, the second difference calculating unit 123,
the second holding unit 124, the second judging unit 125, the
decoding control unit 126, and the recovering unit 127 may also be
included in the reproducing unit 102. For example, the reproducing
unit 102 may include the first holding unit 122 and the second
difference calculating unit 123, and calculate the difference
.DELTA., and the notifying unit 114 may notify the control unit 101
of the difference .DELTA..
Second Embodiment
[0113] In an audio reproducing apparatus in a second embodiment of
the present invention, a reproducing unit, which is constructed in
hardware, controls whether or not: reproduction is to be continued;
and recovery processing is to be performed. This allows the
reproducing unit to perform error detection and error recovery
processing without overloading a control unit.
[0114] First, a structure of the audio reproducing apparatus in the
second embodiment of the present invention shall be described.
[0115] FIG. 5 is a block diagram showing a structure of the audio
reproducing apparatus in the second embodiment of the present
invention. Note that the same elements as those in FIG. 1 share the
same numerical references. Thus, detailed descriptions shall be
omitted.
[0116] An audio reproducing apparatus 200 shown in FIG. 5 decodes
an audio data stream 131 and outputs the decoded audio data stream
131 as decoded audio data 133. The audio reproducing apparatus 200
includes a control unit 201 and a reproducing unit 202.
[0117] The reproducing unit 202 decodes the audio data stream 131,
as well as detects the error therein. The reproducing unit 202 is
constructed in a dedicated circuit (hardware) to the unit. For
example, the reproduction unit 202 is a semi-conductor integrated
circuit structured of one or more chips. The reproducing unit 202
includes an error detecting unit 203 and a decoding unit 104.
[0118] The error detecting unit 203 detects the error in the audio
data stream 131. The error detecting unit 203 includes an
extracting unit 111, a calculating unit 112, a first difference
calculating unit 113, a first judging unit 221, a first holding
unit 222, a second difference calculating unit 223, a second
holding unit 224, a second judging unit 225, a decoding control
unit 226, and a recovering unit 227. Note that the functions of the
first judging unit 221, the first holding unit 222, the second
difference calculating unit 223, the second holding unit 224, the
second judging unit 225, the decoding control unit 226, and the
recovering unit 227 are respectively equivalent to those of the
first judging unit 121, the first holding unit 122, the second
difference calculating unit 123, the second holding unit 124, the
second judging unit 125, the decoding control unit 126, and the
recovering unit 127 shown in FIG. 1
[0119] The control unit 201, which is controlled by software,
controls the reproducing unit 202.
[0120] As described above, the audio reproducing apparatus 200 of
the second embodiment of the present invention is different from
the audio reproducing apparatus 100 of the first embodiment in that
the first judging unit 221, the first holding unit 222, the second
difference calculating unit 223, the second holding unit 224, the
second judging unit 225, the decoding control unit 226, and the
recovering unit 227 are included in the reproducing unit 202
constructed in hardware.
[0121] Next, operations of the audio reproducing apparatus 200 in
the second embodiment of the present invention shall be
described.
[0122] FIG. 6 is a flowchart showing a flow of processing in the
error detecting unit 203.
[0123] Processing from Steps S301 to S303 shown in FIG. 6 is
equivalent to that from respective Steps S101 to S103 in FIG. 3,
thus the description shall be omitted.
[0124] Processing from Steps S304 to S309 shown in FIG. 6 is
equivalent to that from respective Steps S202 to S207 in FIG.
3.
[0125] The first holding unit 222 holds a difference Diff
calculated by the first difference calculating unit 113 at Step
S303.
[0126] The first judging unit 221 judges whether or not position
.alpha. matches with position .beta. (S304). In the case where the
first judging unit 221 judges that the position .alpha. matches
with the position .beta. (S304: Yes); that is, the position .alpha.
shown with a First_access_unit_pointer 157 is correct, the decoding
unit 104, controlled accordingly by the decoding control unit 226,
decodes the audio data stream 132. In other words, the audio
reproducing apparatus 200 continues reproduction processing
(S308).
[0127] In the meantime, when the first judging unit 221 judges that
the position .alpha. does not match the position .beta. (S304: No);
that is, the position .alpha. shown with the
First_access_unit_pointer 157 is not correct, the second difference
calculating unit 223 calculate a difference .DELTA.. Here, the
difference .DELTA. is a difference between a difference Diff_old
which is calculated for an immediately preceding audio packet 150
and is held in the first holding unit 222 and the difference Diff
which has been newly calculated and held in the first holding unit
222 (S305). The second holding unit 224 holds each of differences
.DELTA. calculated by the second difference calculating unit
223.
[0128] Next, the first holding unit 222 holds the newly calculated
difference Diff as a difference Diff_old (S306).
[0129] Then, the second judging unit 225 judges whether or not the
plural differences .DELTA. held in the second holding unit 224 are
constant (S307). Specifically, the second judging unit 225 judges
the audio data stream 131 to be reproducible when the plural
differences .DELTA. held in the second holding unit 224 are
constant; that is, the respective differences .DELTA. between the
plural audio packets to be consecutively inputted are constant
(S307: Yes). Meanwhile, the second judging unit 225 judges the
audio data stream 131 to be irreproducible when the plural
differences .DELTA. held in the second holding unit 224 are not
constant; that is, the respective differences .DELTA. between the
plural audio packets to be consecutively inputted are not equal
(S307: No).
[0130] In the case where the differences .DELTA. are constant
(S307: Yes), the decoding unit 104 decodes the audio data stream
132 by the control of the decoding control unit 226. In other
words, the audio reproducing apparatus 200 continues reproduction
processing (S308).
[0131] Meanwhile, in the case where the differences .DELTA. are not
constant (S307: No), the decoding unit 104, controlled accordingly
by the decoding control unit 226, halts the decoding of the audio
data stream 132. Furthermore, the recovering unit 227 discards once
currently read out data, and performs recovery processing such as
initialization and restart of the reproducing unit 202 (S309).
[0132] Following one of the reproduction continuation (S308) and
recovery processing (S309), the audio reproducing apparatus 200
applies processing shown in FIG. 6 to the succeeding audio packets
150.
[0133] Through the above mentioned process, the audio reproducing
apparatus 200 in the second embodiment of the present invention, as
well as the audio reproducing apparatus 100 in the first
embodiment, judges the value of the First_access_unit_pointer 157
to be unauthorized because either: the value is in the violation of
the standard; or the data is damaged. Thus, the audio reproducing
apparatus 200 in the second embodiment of the present invention can
avoid noise resulting from data shift which is caused by a scratch
on a disc or a transmission error and damages part of data. In
addition, the audio reproducing apparatus 200 in the second
embodiment of the present invention can reproduce the music data
which conventional audio reproducing apparatuses judges to be an
error and does not conform to the standard.
[0134] Furthermore, in the audio reproducing apparatus 200 in the
second embodiment of the present invention, the reproducing unit
202 controls whether or not: the reproduction is to be continued;
and recovery processing is to be performed. As a result, the audio
reproducing apparatus 200 in the second embodiment of the present
invention can perform error detection and error recovery processing
without overloading the control unit 201.
[0135] Note that in the above description, the first judging unit
221 intends to judge whether or not the position .alpha. matches
the position .beta. based on the difference Diff, following the
calculation of the difference Diff (S303). Meanwhile, the judgment
whether or not the position .alpha. matches with the position
.beta. may be made before the calculation of the difference Diff
(between S302 and S303). When the position .alpha. matches with the
position .beta. as the above result, calculation processing for the
difference Diff (S303) may be omitted.
Third Embodiment
[0136] An audio reproducing apparatus in a third embodiment of the
present invention has a function of selectively causing a
reproducing unit and a control unit to control whether or not:
reproduction is to be continued; and recovery processing is to be
performed. As a result, the audio reproducing apparatus in the
third embodiment of the present invention can perform recovery
processing with the most appropriate scheme for the system.
[0137] First, a structure of the audio reproducing apparatus in the
third embodiment of the present invention shall be described.
[0138] FIG. 7 is a block diagram showing the structure of the audio
reproducing apparatus in the third embodiment of the present
invention. Note that the same elements as those in FIG. 1 and FIG.
5 share the same numerical references. Thus, detailed description
shall be omitted.
[0139] An audio reproducing apparatus 300 shown in FIG. 7 decodes
an audio data stream 131 and outputs the decoded audio data stream
131 as decoded audio data 133. The audio reproducing apparatus 300
includes a control unit 101 and a reproducing unit 302.
[0140] The reproducing unit 302 decodes the audio data stream 131,
as well as detects the error therein. The reproducing unit 302
includes a dedicated circuit (hardware) to the unit;that is, for
example, a semi-conductor integrated circuit structured of one or
more chips. The reproducing unit 302 includes an error detecting
unit 303 and a decoding unit 104.
[0141] The error detecting unit 303 detects the error in the audio
data stream 131. The error detecting unit 303 includes an
extracting unit 111, a calculating unit 112, a first difference
calculating unit 113, a notifying unit 114, a first judging unit
221, a first holding unit 222, a second difference calculating unit
223, a second holding unit 224, a second judging unit 225, a
decoding control unit 226, a recovering unit 227, and a mode
selecting unit 341.
[0142] The mode selecting unit 341 selects one of an automatic
recovery mode (a first state) and a second state. Here, the first
state causes the reproducing unit 302 to control whether or not:
reproduction is to be continued; and recovery processing is to be
performed, and the second state causes the control unit 101 to
control whether or not: reproduction is to be continued; and
recovery processing is to be performed. For example, the mode
selecting unit 341, controlled by the control unit 101, selects one
of the first state and the second state.
[0143] In the first state, the first judging unit 221 judges
whether or not a position .alpha. matches with a position .beta..
Here, the position .alpha. is shown with a
First_access_unit_pointer 157 which has been extracted by the
extracting unit 111, and the position .beta. is calculated by the
calculating unit 112.
[0144] In the first state, the second judging unit 225 judges
availability of reproduction for audio data 155 included in the
audio data stream 131 according to change of differences Diff which
are calculated by the first difference calculating unit 113 and
each of which is calculated for respective plural packets 150.
[0145] In the second state, the first judging unit 121 judges
whether or not the position .alpha. matches with the position
.beta.. Here, the position .alpha. is shown with the
First_access_unit_pointer 157 which has been extracted by the
extracting unit 111, and the position .beta. is calculated by the
calculating unit 112.
[0146] In the second state, the second judging unit 125 judges the
availability of the reproduction for the audio data 155 included in
the audio data stream 131 according to change of differences Diff
which are calculated by the first difference calculating unit 113
and each of which is calculated for respective plural packets
150.
[0147] In the first state, the decoding unit 104 decodes the audio
data 155 included in the audio data stream 132 in the case where:
the fist judging unit 221 judges the position .alpha. matches the
position .beta.; or the second judging unit 225 judges the audio
data 155 to be reproducible. In the first state, the decoding unit
104 does not decode the audio data 155 included in the audio data
stream 132 in the case where: the fist judging unit 221 judges that
the position .alpha. does not match the position .beta.; and the
second judging unit 225 judges the audio data 155 to be
irreproducible. In the second state, the decoding unit 104 decodes
the audio data 155 included in the audio data stream 132 in the
case where: the fist judging unit 121 judges the differences Diff
to be constant; or the second judging unit 125 judges the audio
data 155 to be reproducible. In the second state, the decoding unit
104 does not decode the audio data 155 included in the audio data
stream 132 in the case where: the fist judging unit 121 judges the
differences Diff to be not constant; and the second judging unit
125 judges the audio data 155 to be irreproducible.
[0148] Next, operations of the audio reproducing apparatus 300 in
the third embodiment of the present invention shall be
described.
[0149] FIG. 8 is a flowchart showing a flow of processing in the
error detecting unit 303.
[0150] Processing from Steps S401 to S403 shown in FIG. 8 is
equivalent to that from Steps S101 to S103 in FIG. 3, thus the
description shall be omitted.
[0151] After Step S403, the mode selecting unit 341 judges the
audio reproducing apparatus 300 to be one of the first state and
the second state based on the control by the control unit 101.
Here, in the first state, the reproducing unit 302 controls whether
or not: reproduction is to be continued; and recovery processing is
to be performed, and in the second state, the control unit 101
controls whether or not: reproduction is to be continued; and
recovery processing is to be performed (S404).
[0152] In the case of the first state (S404: Yes), the reproducing
unit 302 continues processing from Steps S406 to S411. Note that
the processing from Steps S406 to S411 is equivalent to that from
Steps S304 to S309 in FIG. 6, thus the description shall be
omitted.
[0153] In the case of the second state (S404: No), the notifying
unit 114 notifies the control unit 101 of the differences Diff
calculated by the first difference calculating unit 113 (S405).
Based on the differences Diff notified by the notifying unit 114,
the control unit 101 controls whether or not: reproduction is to be
continued; and recovery processing is to be performed. Note that
processing following Step S405 in the control unit 101 is the same
as that in FIG. 4, and thus the description shall be omitted.
[0154] Through the above operations, the mode selecting unit 341
selects the audio reproducing apparatus 300 in the third embodiment
of the present invention to be in one of the first state and the
second state. In the first state, the reproducing unit 302
calculates a difference .DELTA. and controls whether or not:
reproduction is to be continued; and recovery processing is to be
performed. Meanwhile, the control unit 101 neither calculates the
difference .DELTA. nor controls whether or not: reproduction is to
be continued; and recovery processing is to be performed. In other
words, in the first state, the same processing described in the
above mentioned first embodiment is performed. In the second state,
the control unit 101 calculates the difference .DELTA. and controls
whether or not: reproduction is to be continued; and recovery
processing is to be performed. Meanwhile, the reproducing unit 302
neither calculates the difference .DELTA. nor controls whether or
not: reproduction is to be continued; and recovery processing is to
be performed. In other words, in the second state, the same
processing described in the above mentioned second embodiment is
performed. As a result, the audio reproducing apparatus 300 in the
third embodiment of the present invention can perform error
recovery processing with the most appropriate scheme for the system
by providing an interface of which an operation mode is
addressable.
[0155] Note that in the above description, the control unit 101
intents to perform the processing in the FIG. 4 of the second
state. In the meantime, part of processing in FIG. 4 may be
performed by the reproducing unit 302. For example, in the second
state, the reproducing unit 302 may perform processing up to the
calculation of the differences .DELTA. (S408) and notify the
control unit 101 of the differences .DELTA.. Here, the control unit
101 may judge whether or not the differences .DELTA. are constant
(S205) and perform the following processing.
[0156] In the above description, the mode selecting unit 341
selects one of the first state and second state. In addition, the
mode selecting unit 341 may select two or more states. For example,
as described above, the reproducing unit 302 may additionally
perform processing up to the calculation of the differences .DELTA.
as a third state.
[0157] Moreover, in the above description, the control unit 101
intends to include the first holding unit 122 and the second
holding unit 124; however, the first holding unit 122 and the
second holding unit 124 may be omitted. In the second state as
well, for example, the differences Diff calculated by the first
difference calculating unit 113 may be held in one of the first
holding unit 222 and a holding unit (such as a RAM) which is
included in either the reproducing unit 302 or the audio
reproducing apparatus 300. Furthermore, the differences .DELTA.
calculated by one of the second difference calculating unit 123 and
the second calculating unit 223 may be held in the holding unit
(such as a RAM) which is included in either the reproducing unit
302 or the audio reproducing apparatus 300.
[0158] Further, in the above description the control unit 101
intends to include the first judging unit 121, the first holding
unit 122, the second calculating unit 123, the second holding unit
124, the second judging unit 125, the decoding control unit 126,
and the recovering unit 127; meanwhile, depending on a system, the
control unit 101 may omit some or all of the first judging unit
121, the first holding unit 122, the second calculating unit 123,
the second holding unit 124, the second judging unit 125, the
decoding control unit 126, and the recovering unit 127. For
example, in the case where only the first state is used, the
control unit 101 may omit the first judging unit 121, the first
holding unit 122, the second calculating unit 123, the second
holding unit 124, the second judging unit 125, the decoding control
unit 126, and the recovering unit 127.
[0159] Although only some exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention.
INDUSTRIAL APPLICABILITY
[0160] The present invention can be applied to audio reproducing
apparatuses, in particular, to an audio reproducing apparatus which
reproduces Linear PCM music data.
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